Re: GPT boot has less features than legacy MBR-based one (Was: UEFI, loader.efi and /boot.config)

On Fri, Jan 18, 2019 at 2:11 PM Emmanuel Vadot <manu_at_bidouilliste.com>
wrote:

> On Fri, 18 Jan 2019 22:50:31 +0300
> Lev Serebryakov <lev_at_FreeBSD.org> wrote:
>
> > On 18.01.2019 22:35, Rodney W. Grimes wrote:
> >
> > >>> errm.. you press a key and enter device and or loader path. if it is
> not working - the code is there to be fixed.
> > >>  And loader looks to "bootme" attribute and try to boot from partition
> > >> which has one, even if it is loaded from other partition itself.
> > >>
> > >>> GPT does not have the concept of active partition.
> > >>  It has "bootme" / "bootonce" attributes. And [zfs]gptboot doesn't
> have
> > >> any tools to set these attributes, AFAIK. Same for UEFI boot code.
> > >
> > > The gpart(8) command is used to set/unset these.
> >  gpart need booted system. NanoBSD typically have two "system"
> > partitions, "old" (previous) and "new" (current). After upgrade they
> > switched (new code is written to "previos" partition and bootable
> > atteibute is set to it, "active" in case of MBR and "bootme" in case of
> > GPT).
> >
> >   If this new partition has problems and could not be booted, it is hard
> > to boot from "old" (previous) one. MBR + boot0 could (interactively)
> > change active partition before system is booted, and this problem could
> > be solved with one keypress: you select old partition on boot.
> >
> > --
> > // Lev Serebryakov
> >
>
>  With UEFI Boot* variable you could do :
>
>  - Update previous partition and set BootNext to it
>  - If it fail next boot will be on current partition due to BootOrder
>  - If it succeed, change the BootOrder to have the new partition first.
>

Also most UEFI BIOSes I've used (which isn't a lot) allow one to choose
which BootXXXX variable to use to boot. Some will even create new BootXXXX
variables that they use when you choose a raw device to boot from.

There's other people that have efi programs that will pop up a menu for you
to select a particular BootXXXX to use. They then set BootNext and exit.
I've not used any of these personally.

But this whole thread tells me we need to rewrite the boot section of our
handbook.

Warner